1. Field of the Invention
The present invention pertains to fluid moving systems for moving fluid from one place to another. In the specific application of the invention to be described hereinafter, the invention relates to a submerged pumping system for elevating high viscosity oil from an underground formation through a well to the well surface.
2. Description of the Prior Art
A variety of types of pumps and artificial lift schemes are in use for producing oil and other liquids from wells where the liquids flow slowly or will no longer flow at all by natural lift. The type of pump selected for use on a particular well is dictated by a number of factors, including the formation pressure and the liquid to be pumped.
Gas lift valves are a well known and efficient means for artificially raising oil to the surface. Submerged mechanical displacement pumps, operated from the surface by reciprocating sucker rods, are also conventionally employed to elevate oil to the well surface, especially where a gas lift installation cannot be used or is not desirable. As compared to gas lift systems, mechanical pumping systems are undesirable to the extent that they entail substantial movement of metal parts which corrode and abrade. Mechanical pumps also produce a relatively limited volume of oil during each pumping cycle and require relatively large amounts of power for their operation. The close tolerances required in most piston-cylinder type mechanical pumps also make such pumps expensive to produce and maintain.
Flexible displacement member or bladder pumps have also been used in various installations for bringing underground oil to the surface. These pumps, which use a distendable diaphragm, bladder or bellows to displace the pumped liquid from a confined area, are particularly useful in wells where the liquid is corrosive or abrasive. Prior art flexible member pumps are usually powered by a mechanically driven piston-cylinder assembly in which the piston acts against a liquid which in turn controls movement of the flexible member. The piston itself is either operated through a mechanical linkage extending from the surface or it is operated by a motor located adjacent the pump. Such systems suffer to a degree from many of the same shortcomings which exist in a conventional mechanical displacement pump. Those systems which require a submerged motor are undesirable in many oil well installations. When used with high viscosity oil, conventional mechanical linkage pumps are inefficient since the density and viscosity of the oil make it difficult to raise the mechanical linkage on the upstroke and prevent the linkage from falling freely during the down stroke.